One of the most widely used electronic devices especially in digital integrated circuits ("ICs") is the metal-oxide semiconductor ("MOS") transistors. MOS transistors are characteristic in that the gate electrode of a MOS transistor is a metal such as aluminum (Al) and the electrode is isolated from the channel by an insulator such as silicon oxide (SiO.sub.2). One of the most important parameters associated with MOS type transistor is the threshold voltage ("V.sub.T "). V.sub.T is the voltage needed to turn on the transistor. That is to say, V.sub.T is the minimum voltage at which electrons begin to move from the source of the transistor to the drain, allowing the transistor to conduct electricity.
The current process by which ICs are developed and produced by manufacturers is shown in the flow diagram of FIG. 1. As shown, an IC is initially designed in step 10 with expected V.sub.T values obtained during the design stage of the device. Then in steps 12-16, V.sub.T adjustment processing is performed on a wafer using various known methods such as photoresist patterning, ion implantation, and heat treatment to set the V.sub.T obtained during the initial design of the device. Typically, steps 12-16 can take anywhere from one to three months to complete because of the time consuming processes involved in creating the wafer, the mask, and the adjusting procedure.
Once the V.sub.T adjusting process is complete, a diagnostic test is performed in step 18 to determine whether the operating parameters of the processed wafer meet specified requirements. Specifically, testing is performed on each area of the processed wafer to determine if the V.sub.T values initially obtained during the design stage work on actually fabricated ICs. If the test fails on any part of the wafer, new values of V.sub.T are calculated as shown in step 20 for the failed areas. Consequently, new V.sub.T adjustment masks are designed and produced as shown in step 22, and the whole process begins again using the new mask with a new wafer. Each time a V.sub.T adjustment has to be made, the entire process as shown in FIG. 1 must be repeated until the processed wafer passes the test at which point the successful processing parameters are used to mass produce the designed device.
As one can imagine, this process of adjusting V.sub.T is long, tedious, and very costly since each run must start with a new wafer and the run takes anywhere from one to three months to complete. Hence, a simpler, faster, and less expensive method is needed in adjusting V.sub.T values of an IC device.